We propose to extend the functionality of our commercial quantum chemistry program, Q-Chem, to effectively treat molecules containing transition metals. This enhanced capability will provide Q-Chem's end-users with the ability to accurately model complex molecules such as proteins, enzymes, and catalysts of industrial importance. While remarkable progress has been made over the last several years in the accurate modeling of systems containing transition metals, current numerical methods for achieving SCF convergence in these systems are problematic at best, resulting in long execution times or, in some cases, complete failure to find a solution. However, a novel computational technique developed at Q-Chem has been shown to dramatically improve convergence for organic molecules with known SCF convergence problems. We propose to adapt this method for use with transition metals. Our goal is to achieve the same robust SCF convergence that is realized for most organic molecules, thereby greatly increasing productivity and extending the capability of scientists to study molecules such as enzymes and industrial catalysts. During Phase (I, our efforts will be to further extend Q-Chem's capability in the molecular biology arena. This proposal seeks to improve the quantum chemical treatment of molecular systems containing transition metals. Transition metal elements are essential to natural biological processes. The technology developed in this research will enable the computer modeling of those systems that are difficult to handle with the current methodologies and therefore increase of the applications of computational modeling. PROPOSED COMMERCIAL APPLICATION: Transition-metal elements play a vital role in biological systems. The success of this project will improve the performance of modeling of transition-metal complexes and making the modelings possible for the systems that current algorithms fail. The resulting work will be made available to researchers in health industry and universities through our commercial software Q-Chem.